Field of the Disclosure
This disclosure relates to methods and systems for diluting a dose of a substance to be delivered to a patient and for determining a maximum deliverable dose of the substance and/or a partial fluid volume to be delivered to the patient to provide a desired dose amount.
Description of Related Art
Many medical procedures require the delivery of a fluid to the patient. Most of the time, the full volume of fluid provided is injected into the patient, with some fluid volume remaining in the fluid reservoir or fluid path. This remaining amount is commonly called the priming volume, dead space volume, retained volume, or non-deliverable volume. This priming volume is often insignificant because it is either small compared to the total volume being delivered or because extra fluid is provided and only the prescribed volume is delivered to the patient. Any extra fluid, including the priming volume, is thrown away after the delivery of the prescribed, desired, or programmed volume is completed. This procedure works well when the fluid is a known, consistent concentration and the prescription is for a volume which is less than the total provided or initial volume.
In some cases, such as nuclear medicine, biologic treatments, or cell therapies, the fluid volumes provided or to be injected are small enough that the dead volume in the fluid path or container may be significant. In nuclear medicine it is common to measure the residual dose in the syringe, needle, and other fluid path elements after the fact, and record that information on the patient's chart along with the initial dose, so that it is possible to compute the delivered dose at a later point in time if it becomes necessary. One approach to improve this situation is to dilute the fluid so that the total volume is increased sufficiently to increase the deliverable amount of the medicine or agent. It then becomes a challenge to know what volume to inject if the whole diluted volume is not to be injected at one time. It also is a challenge to know the total dose that could possibly be injected given the existence of dead space in the fluid path. Specifically, the post dilution concentration of the diluted drug depends upon the initial volume of the drug and the volume of the diluent. An apparatus and system for injecting a small volume of a therapeutic or contrast agent to a patient is discussed in PCT Application No. PCT/US2014/029152 to Uram et al. (published as Publication No. WO 2014/144651), which is assigned to the assignee of the present application, and the disclosure of which is incorporated by reference in its entirety.